1. Field of the Invention
The invention relates to a wavelength converting device such as an SHG device.
2. Related Arts
Non-linear optical crystals, such as lithium niobate or lithium tantalite, have a high second-order non-linear optical constant. It is thus possible to realize a quasi-phase matched (QPM) type second harmonic generation (SHG) device, by providing a periodic polarization domain inversion structure in the crystal. Further, an SHG device of a high efficiency can be realized by forming a waveguide in the periodic polarization domain inversion structure, and the device finds a wide variety of applications such as optical communication, medical uses, optochemical uses, various optical measurements, etc.
The applicant disclosed a process of producing a ridge-shaped optical waveguide used for a device for generating second harmonic wave, in Japanese Patent publication H09-269430A. The waveguide is formed by subjecting an oxide single crystal to ablation working using an excimer laser. Such oxide single crystal includes lithium niobate and a lithium niobate-lithium tantalate solid solution.